1. Field of the Invention
The present invention relates to an image scanning apparatus. More particularly, the present invention relates to a scanner module using a light emitting diode as a light source and an image scanning apparatus employing the same.
2. Description of the Related Art
A scanner module may be employed in an image scanning apparatus, e.g., of a scanner, a copy machine, a facsimile, a multi-functional peripheral device, or the like. The scanner module may be placed, e.g., underneath a document window or platen onto which an original document to be scanned is loaded, and converts the image information read from the document into an electric signal.
A scanner module may include, e.g., a light source generating light, an image sensor that produces electrical signal based on the light reflected from the object to be read. A scanner module may also include a reflection mirror and a condenser lens, which may be aligned in an optical path formed between the light source and the image sensor. A linear light source, such as, e.g., a CCFL (cold cathode fluorescent lamp) or a xenon lamp has been used as the light source in some legacy scanner modules.
However, a CCFL may require a long initial start-up time, which may result in longer time to perform an initial scanning operation. In addition, since the CCFL may contain mercury (Hg), which may have adverse impact on the environment. Further, gas activation rate may be lower, possibly degrading image quality, at lower temperatures. A xenon lamp may generate high-temperature heat, which may degrade the image quality, and can be expensive, resulting in the price competitiveness of the scanner module to suffer.
Recently, there have been suggestions for the use of a point light source, such as a light emitting diode, along with a light guide to serve the role of a linear light source by allowing the light from the point light source to be diffused and/or directed along the scanning width, e.g., across the width of the document or object to be scanned.
As shown in FIG. 1, a light guide member 2 employed in a scanning module may have a predetermined width in the image scan direction and a predetermined length in the sub-scan direction (i.e., direction substantially perpendicular to the image scan direction). The light guide member 2 may also include an exit surface 2a facing the object to be scanned, a reflective surface 2b formed on the opposite end of the exit surface 2a to reflect and diffuse the light generated from a light source 1, and guide surfaces 2c formed on both sides of the light guide member 2 to connect the exit surface 2a to the reflective surface 2b. The guide surfaces 2c may be inclined relative to the reflective surface 2b such that the light reflected from the reflective surface 2b can be directed toward the exit surface 2a of the light guide member 2.
As shown in FIG. 2, the reflective surface 2b of the light guide member 2 may include a plurality of reflective grooves 2d, which extend widthwise, parallel to each other, along the light guide member 2, so that the light generated from the light source 1 may be reflected and diffused by the reflective surface 2b, and then may be guided toward the exit surface 2a of the light guide member 2. FIG. 3 shows an example of a distribution of light, which is irradiated onto the surface of a document to be scanned from the light guide member 2, across the image scan direction. As illustrated in FIG. 3, unfortunately, when a point light source and light guide structures shown in FIGS. 1 and 2 result in the light distribution to be non-uniform, making it difficult to accurately read the object being scanned.